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Science: Solar neutrino problem still unsolved

By KEN CROSWELL

Last month, an American astronomer claimed to have finally solved the
longstanding solar neutrino problem. But his explanation of why the Sun
generates fewer neutrinos than standard theories predict is totally wrong,
say two other astronomers.

Robert Kurucz of the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Massachusetts, had suggested that electrons might speed up nuclear
reactions in the Sun’s core, allowing the Sun to generate its energy at
a lower temperature than is assumed by standard models (New Scientist, Science,
21 March). Because the core temperature was lower, the flux of neutrinos
would also be lower, explaining the shortfall of neutrinos detected by several
separate experiments on Earth.

But Kurucz’s ideas are neither original nor correct, say John Bahcall
of the Institute for Advanced Study in Princeton, New Jersey, and Edwin
Salpeter of Cornell University. In a blistering attack, Bahcall and Salpeter
accuse Kurucz of sloppy scholarship and faulty calculations.

Bahcall and Salpeter say that all the effects that Kurucz talks about
have been known by theorists for decades and are already incorporated into
standard models of the solar interior. In particular, the scientists say
that electrons do indeed shield protons and speed up nuclear reactions,
as Kurucz claims, but that the effect is small. Salpeter himself studied
this phenomenon back in the 1950s.

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Kurucz also claims that a nuclear reaction between two protons and an
electron may increase rather than decrease the rate at which the Sun generates
energy. But the effect is tiny, and Bahcall says he evaluated it in the
1960s.

Furthermore, Bahcall and Salpeter say that Kurucz has done his calculations
wrong, because he treats electrons as particles. According to quantum mechanics,
electrons travel as waves. This mistake leads to an error of a factor of
a million million, say Bahcall and Salpeter.

Bahcall and Salpeter do not plan to publish their report. ‘There is
nothing new in the proposals by Kurucz,’ they say. Instead, Bahcall and
Salpeter are distributing to other astronomers a three-page preprint in
which they discuss in detail the errors and give references to past work
that correctly computes how electrons affect nuclear reactions in the Sun.